1. Field of the Invention
The invention relates to a steer-by-wire steering system.
2. Description of Related Art
In a vehicle steering system that is described in Japanese Patent Application Publication No. 2001-114123 (JP 2001-114123 A) as a steer-by-wire steering system, a rotating operation member and wheels are not mechanically coupled to each other. A steering actuator, which is controlled on the basis of a rotating operation amount of the rotating operation member, steers the wheels. In the above-described steer-by-wire steering system, a configuration for detecting the rotation of the rotating operation member is important. When a malfunction occurs in the above-described configuration, steering is disabled even if the steering actuator is properly operable. In the configuration for detecting the rotation of the rotating operation member, which is described in JP 2001-114123 A, only one angle sensor is provided. In a steering system described in Japanese Patent Application Publication No. 10-278826 (JP 10-278826 A), in order to increase the redundancy of the above-described configuration, a main steering angle sensor and a backup steering angle sensor are provided. Therefore, with the steering system described in JP 10-278826 A, even if a malfunction occurs in the main steering angle sensor, it is possible to continue steering with the use of the backup steering angle sensor.
In the steering system described in JP 10-278826 A, the two identical steering angle sensors are provided in order to make it possible to continue steering even if a malfunction occurs in one of the steering angle sensors. As a result, the number of components and the cost are unnecessarily increased.